The present invention relates to vessel or pipeline closures, which selectively enclose and seal an interior portion of a pressure containing vessel or pipeline. More particularly, the methods and systems of this invention relate to closures such as the type used on pipeline pig launching and receiving systems, and closures on access portals for pressurized vessels. The methods and system of this invention may improve safety, closure life expectancy and functional operation.
One function of a closure is to allow relatively convenient and potentially routine access to the interior of a pressure-containing vessel or volume. Pipelines are commonly cleaned and/or inspected by launching pipeline xe2x80x9cpigsxe2x80x9d into a portion of the pipeline system and then recovering the pig and accumulated debris at a receiving point. An end portion of the pig launchers and receivers are commonly capped with a closure. A pipeline closure is essentially a selectively operable door to the pipeline that securely contains pressure within the pipeline when the closure is closed and sealed.
Closures also may be included on volumetric pressurized vessels to provide access to an interior portion of the vessel. The vessel typically carries a high pressure therein, such as from less than one-hundred psig to in excess of 1000 psig. Closures may be found in a range of nominal sizes corresponding with pipeline sizes and vessel access port sizes. Common sizes range from 2 to 14 inches, but smaller and larger closures are also known. These closures are commonly manufactured substantially from metallic materials in a closed die forging process.
Closures are composed of basically two components, a hub and a cap. The hub may be secured to the vessel or pipeline, typically by welding or threading. The hub may include a threaded portion including an external/male thread, such as a relatively heavy-duty ACME thread to mate with the cap. The cap may cover the access port to the vessel, and may removably secure to the hub. The cap may include an internal/female thread for threadably mating the cap with the hub.
An O-ring or other sealing member may be included to seal against leakage of pressurized vessel/pipeline contents between the cap and the hub. Heavier closures may also include a hinge and/or support members, such as a pivoting swing-arm to assist with manipulation of the cap when disconnected from the hub.
Prior art closures are commonly constructed with xe2x80x9chammer lugsxe2x80x9d or xe2x80x9cwingsxe2x80x9d on an external portion of the cap to allow the cap to be tightened to and loosened from the hub via hammer blows on the lugs. In some instances, such practice may be performed with relatively heavy hammers.
Although the cap is commonly made from relatively ductile steel, the hammer blows may leave marks on the cap and result in deformation of the lugs. With continued use, the lugs may substantially deform and the metal material on the lug may begin to fold back or xe2x80x9ccauliflowerxe2x80x9d. Such hammering cold works and embriffles the material of the xe2x80x9chammer lugxe2x80x9d. The hammer blows may result in ejection of small pieces of metal from the lug or cap traveling at extremely high velocities. Such material may pose a severe safety hazard with lug-type closures. These projectiles of varying size may result in injury to eyes and skin penetration of persons near the struck lug. Routine maintenance may be required to file down sharp edges and remove deformed lug material to reduce the likelihood of such occurrence.
An additional safety hazard with lug type enclosures includes the generation of sparks when struck by metal hammers. Under certain conditions, such as when the vessel/pipeline contains flammable material, or in a classified environment, such as in an enclosed building or a confined area, it may desirable, if not required, to avoid the generation of any sparks. In such instances, the use of a lug type closure may require the use of special hammers, such as brass or rubber.
An additional problem with metallic lug-type closures may result from hammer impacts. The cap material, particularly in and near impacted areas, may develop stress cracks. Such cracks in the work hardened material may reduce the safety, reliability and working strength of the cap. Particularly in the presence of corrosive gasses or liquids, corrosion cells or sites may initiate within microscopic cracks. In cold climates, the cap material may also become more brittle and even more susceptible to generation of flying particles and creation of stress-fractures.
The disadvantages of prior art are overcome by the present invention. An improved closure and closure method eliminating the need to tighten and/or loosen the closure via hammer blows are described herein.
This invention provides methods and systems for constructing a vessel or pipeline closure, which is relatively simple to operate, reliable and cost effective. The closure of this invention may eliminate hammering on the lugs to tighten or loosen the closure. This closure may be tightened and/or loosened by applying a substantially linear force tangentially to a radially outward portion of the cap.
In one embodiment, a nut and bolt system may be provided which may be utilized to selectively apply the tightening force and/or the loosening force, utilizing the same nut and bolt system.
It is an object of this invention to provide a closure that improves closure safety. The optionally lugless closure of this invention may eliminate lug-hammering and the detrimental effects associated therewith.
It is an object of this invention to provide a closure that improves closure operation. The tightening and loosening methods and systems of this invention provide a safe, reliable and effective closure operation.
It is a feature of this invention that the opening and closing apparatus may improve closure safety by preventing the closure from prematurely loosening during closed service.
It is a feature of this invention to provide a closure system, which is relatively simple to operate and may not require any special tools or skills for its operation.
It is also a feature of this invention that the closure may be utilized in hazardous environments, classified areas, or other locations where the generation of sparks and/or flying metal particles may lead to detrimental ignition or other bodily injury.
It is a further feature of this invention that existing closures may be altered or retro-fitted to incorporate this invention.
An additional feature of this invention is that when the cap is tightened to the hub, the pulling assembly used for tightening the cap may remain secured in place, engaged with the tightening pulling ear to maintain the cap securely tightened with the hub. Thereby, inadvertent loosening, such as by impact or thermal changes, may be precluded.
It is an advantage of this invention that, due to the possible elimination of hammering, the closure cap may not be subjected to hammering forces which might otherwise create stress cracks or work-hardening.
It is also an advantage of this invention that the closure cap may still be externally supported by hinges or supports, when the cap is opened.
It is a further advantage of this invention that maintenance such as may be required to maintain hammer lugs in a safe condition may be reduced or eliminated.
It is yet another advantage that a closure according to this invention may also be fabricated and/or purchased at a cost not substantially different from prior art closures.